—2 Timothy 3:14-17 (NASB)
How is it that the Bible—here referred to as "the sacred writings"—"are able to give you the wisdom that leads to salvation through faith"? Isn't "faith" predicated on something that can't be seen or proven?
As I've stated many times, the Greek and Hebrew words for "faith" can also be translated "faithfulness". God's Word provides the guidelines for how to be completely faithful, never straying from His ways or path. Sticking to this path—and so obtaining your eternal reward—is the ultimate biblical definition of "wisdom".
The varied application of God's Word identified here by Paul—"teaching", "reproof", "correction", and "training in righteousness"—all describe aspects of keeping us on God's path. But they have the dual pupose of not just making us into an individual, faithful follower of Christ, but "adequate, equipped for every good work". In other words, faithfulness enabled by our commitment to God's Word empowers our successful service to and for Him.
The key phrase for Christians is "all Scripture". Don't limit your self to just the New Testament nor ignore the difficult things like genealogies or prophetic messages. Every word, sentence, chapter, and book is "profitable" and every one of them is needed to make us "adequate" and "equipped". We need it all.†††